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Bagasse particle is used in energy generation, and the usual method for determining their size distribution is sieving. Traditional methods for measuring the bagasse particle size distribution, such as sieving, do not evaluate the effect of the irregular particle shape, producing results that are not always applicable to the prediction of fluid dynamic behavior. This work determined size distribution of bagasse particles considering their aerodynamic behavior. Physical-chemical characterization was performed in different particle sizes of the bagasse. A particulate elutriation and settling system was developed to determine the terminal velocity distribution of particles. Drag coefficients and terminal velocities measured were compared with literature correlations. Almost all the correlations analyzed showed significant deviations from the values obtained experimentally. Haider and Levenspiel’s correlation showed the smallest average deviation. Two types of particles were observed in bagasse: fibers and spongy pith. The apparent density of the particles depends on the particle size, and the ash concentration in smaller fractions is 3 times larger than the average. The method of aerodynamic separation for the characterization of bagasse particle allowed to obtain information that cannot be found by the traditional method of separation by sieving.

Biomass-derived carbons are among the most promising candidates for large-scale electrochemical-energy-storage devices owing to their low cost, sustainability and widespread resources. Herein, the authors report a simplistic synthesis process for preparing two types of biomass carbons derived from cassava stalks and bamboo consisting of direct pyrolysis of the ground samples at 750°C for 4 h. The electrochemical performances of the prepared biomass carbons are investigated in supercapacitors and lithium-ion battery (LIB) systems. Both the cassava and bamboo samples possess a high graphitization degree and good surface wettability as demonstrated by X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. As a supercapacitor electrode, cassava-derived carbons show the best performance with a maximum specific capacitance of 212 F/g and capacity retention of 95% after 2000 cycles. Moreover, as an electrode material for LIBs, cassava-derived carbons demonstrate the highest charge capacity of 357 mAh/g (at 100 mA/g), which stabilizes at 254 mAh/g. This approach shows great potential to achieve advanced electrode materials from low-cost, green and industrial-grade production of biomass-derived carbon materials by simple synthesis for advanced energy-storage applications in the future compared with conventional approaches.

The demand for using wireless sensors to monitor gases dissolved in transformer oil is growing and has brought challenges in the development of new sources of energy. Nano-generators are devices capable of converting mechanical energy, as vibrations, into electricity in a innovative and renewable way at low cost. In this work, the authors studied the addition of a steel spring to triboelectric nanogenerator (TENG) on the performance of its output power. Here, TENGs were built by using ZnO nanorods as donating electrons and PDMS:GO composites as negative material. PDMS:GO composites were prepared at different concentrations and the study was carried out in a wide frequency range (45 to 250 Hz). The addition of a steel spring to design of the TENG, as well as, 4% weight GO to PDMS improved the performance of the device. A power density around 246 mW m−2 , and output voltage of 4 V were obtained at 60 Hz. TENG’s ability to collect vibration energy from the wall of transformers and transform it into electrical energy is discussed based on the vibration frequencies obtained at different external points of transformers and performance of the devices.

A one-dimensional mathematical model of the fluid dynamics and combustion process in a bubbling fluidized bed was developed. In the bubble phase, the model includes the throughflow and bypass flow, which crosses the bed without taking part in combustion because of the preferential bubble paths expected in large fluidized-bed systems. Unlike in the classic approach, the emulsion phase was considered not to remain under minimum fluidization conditions, and the influence of downward particles was considered. A correction factor for the equation of the mass transfer coefficient previously described by other authors was therefore proposed to take into account the bypass flow expected in large systems. The main results provided by the model are the velocities and volumetric flows of the gases in the bed (emulsion, visible bubble and throughflow gases), the mass transfer between bed phases and the oxygen profile in the bed.

Bio-oil produced by fast pyrolysis of eucalyptus sawdust in a bubbling fluidised bed reactor with temperature between 450 and 550 °C was divided into two fractions: heavy bio-oil (HBO) and light bio-oil (LBO). These fractions were mixed with ethanol (EtOH) in order to obtain seven ternary mixtures. These mixtures were characterised according to the following properties: viscosity, lower heating value (LHV), higher heating value (HHV), water content, solids content, acidity, flash point, pour point, density and ultimate analysis. Fractions also had their properties determined. Viscosity, due to its peculiarity, was monitored until 90 days and each mixture had its viscosity profile as a function of time and temperature. Ultimate analysis, heating values, acidity and water content were determined at two different moments to provide an understanding into mixtures ageing. Some properties were analysed through the ternary diagram. Overall, mixtures presented good fuel characteristics with lower water content and acidity and higher heating values and carbon content than typical bio-oil. Nevertheless, choosing HBO as the main component had its drawbacks like viscosities unexpectedly high. Except for viscosity, ageing promoted beneficial changes like lowering water content to a minimum of 0.93% and raising HHV to a maximum of 24.6 MJ kg−1.

This study presents the results of audits of social responsibility management systems according to SA 8000 standard carried out in 35 units of seven Brazilian organizations, in the fields of construction industry, financial institution, sugar and alcohol industry, printing, telemarketing and public administration, totaling 230,561 workers in the audited scopes, addressing medium and large size companies. An analysis of the main points of improvement and items associated with the difficulties of implementation and management was carried out, verifying that the requirements of SA 8000:2008 with lower adherence in terms of non-compliance are: “Item 3 Occupational health and safety”€, the item with the greatest difficulty of attendance in all segments and sizes of organizations, and the second largest item not met was the qualification and control of suppliers. As organizations, to obtain certification, must correct these problems and solve the requirements that their suppliers do not meet, this causes a great impact in the supply chain of these companies, since the suitability is extended to subcontracted companies impacting working conditions and increasing the degree of compliance with legislation throughout the production chain, with the improvement of working conditions in subcontracted companies, where often the working conditions are not adequate and legislation is not met. These results demonstrate the need to make social responsibility management systems more efficient, investing in actions to address non-compliances and improve management throughout the supply chain.

This work investigates the thermal degradation of leaves from the Amazon Rainforest litter, which is currently unknown. It formulates innovative thermal degradation equations useful for numerical simulation of wildfires in this biome. Furthermore, this work quantifies for the first time structural and non-structural components of litter leaves, which translates into an improved representation of the thermal degradation process. The main output of this work is the reaction mechanism with six parallel independent reactions for soluble sugars, pectin, hemicellulose, cellulose, lignin, and other organic compounds, which represent the thermal degradation of the litter leaves. The average composition of the Amazonian litter leaves is soluble sugars 22.9%, pectin 9.0%, hemicellulose 18.3%, cellulose 9.1%, lignin 21.2%, and inorganic plus other organic compounds 19.5%.

An overview of planted forest and its use for energy generation in Brazil is presented. Historical and current data on planted area, productivity and consumption of planted wood is presented. Planted wood was responsible for 7.8% of primary energy consumed in Brazil during 2016, mainly as charcoal for steel industry. Eucalyptus and pine are the main planted species in Brazil. Favourable climate and soil quality enhance productivity of planted forest in Brazil, reaching 30 to 36 m3 ha−1 y−1 thus representing the world’s highest productivity, with better managed forests producing up to 70 m3 ha−1. Forest residues reach 20% for eucalyptus and 40% for pine as compared to the amount of wood produced. Residues of a particular eucalyptus planted forest were collected directly on the field, considered for fuel and analyzed determining composition, heat value, ash content and thermogravimetric analysis. It is estimated a yearly generation of 20 × 106 t of forest residues and 15 × 106 t of wood industry residues.

The scope of this paper is to make a feasibility analysis for energy production from sugarcane byproducts in Peru. Therefore, it is shown the history, methods, current scenario and future prospects of sugarcane plantations related to the ethanol industry and the sugar industry. There will be shown analysis of harvest residues (top and leaves). Bagasse is a mill residue, produced after sugarcane juice is extracted from the sugarcane. Nowadays this residue is burnt in boilers and this energy is used to generate steam. In the other hand, harvest residues represent a significant part of the energy contained in the sugarcane, but it is left in the field, or worse; burnt before the harvest. There will also be shown an estimated value of the electricity generation potential from sugarcane residues.

A simple numerical model is presented to simulate the combustion of a biomass particle in a vertical stream. Emphasis focuses on the trajectories of spherical and cylindrical particles in the furnace. Combustion is modeled in three sequential stages: drying, pyrolysis and char combustion. Biomass consumption is determined by correlations based on Arrhenius kinetics and mass transfer parameters. Pyrolysis is modeled using five first-order kinetic equations considering the following products: volatiles, char and tar. The char consumption rate is modeled by three first-order kinetic equations, considering that char reacts with oxygen, carbon dioxide and water. The model is validated by comparing the duration of each simulated stage against experimental data taken from the literature. It is validated for spherical particles of up to 5 mm in diameter using a shrinking core model and for cylindrical particles of up to 3 mm using an ash-segregated model. Particle trajectory results are presented in order to determine the geometry and functional parameters of the combustion chamber that ensure complete suspension-firing. The combustion chamber geometry and biomass distributor height are determined as a function of airflow velocity and biomass characteristics for the combustion of bagasse with moisture contents of 30%–50% and particle diameters of 0.5 mm–3.5 mm. This study also allows the airflow velocity to be determined based on the boiler dimensions and the biomass characteristics to ensure that no particle ends up on the grate. After establishing the velocity, it is possible to determine what particle size will reach the top of the chamber or burn completely in suspension.

This work estimated the energy consumption of three straw-collection systems: baling, forager and whole-plant harvest system in which the chopped cane and straw are separated at the mill. About 12 t ha −1 yr −1 of straw can be collected for a typical sugarcane yield of 100 t ha −1 yr −1 . The system with the lowest energy consumption was whole-plant harvesting, which used 2.0 L of diesel fuel per tonne of straw collected for a harvest area 30 km from the mill and when 75% of straw is collected. This value is approximately 40% lower than of the specific consumption estimated for the other systems and just 1–2% of the energy available from the straw. However, for successful application of the whole-plant harvest system, it is needed significant improvements to the efficiency of cane cleaning systems for straw separation. The thermal energy available from the straw when 75% is recovered is 182 GJ ha −1 yr −1 , compared to 151 GJ ha −1 yr −1 of the ethanol that can be produced and approximately 174 GJ ha −1 yr −1 from the bagasse. If cane straw were used for electricity generation, an additional 12.6 MWh ha −1 yr −1 could be generated.

In this work, were studied the thermal and kinetic characteristics of the palm kernel shell (PKS) and empty fruit bunch (EFB) from the African oil palm. Experiments in the inert atmosphere were carried out in a thermogravimetric analyzer. In the kinetic analysis were applied the one-step reaction through iso-conversion methods, mechanism of independent parallel reactions (MIPR), and mechanism of consecutive reactions (MCR). The one-step reaction mechanism overestimated the thermal decomposition of all samples; however, the best was the EFB. The MIPR showed to be representative of the thermal decomposition of all samples, and the proposed correlations between the pre-exponential factor and the heating rate improved the accuracy of the model. The MCR analysis showed that using the same kinetic parameters applied in the MIPR does not affect reliability. Finally, as a conclusion, blending PKS with EFB increase 5% heating value and decrease 50% ash content.

Spray towers allow for controlling air pollution in which a liquid is sprayed in small droplets to produce a large interfacial area for mass transfer between a gas and a liquid phase. An experimental study of a spray tower for removing SO2 is described. The experiments were carried out under different operating conditions by varying the gas velocity, liquid flow rate, and SO2 concentration. SO2 removal efficiency, volumetric mass transfer coefficient, and liquid-film formation as a result of the collision of droplets against the tower wall are investigated. Removal efficiency and volumetric mass transfer coefficient are analyzed as a function of gas velocity, liquid flow rate, and SO2 concentration, while liquid-film formation is evaluated as a function of tower height. The results indicate high removal efficiency. Correlations to predict the volumetric mass transfer coefficient are also proposed.

This study sought to quantify and characterize cassava waste as fuel. The wastes from three cultivars were collected to study and were divided into three distinct parts of the cassava plant: seed stem, thick stalks, and thin stalks. Physical and chemical analyzes were carried out to determine the elemental composition of the waste: volatile matter; fixed carbon; ash; moisture; lignin; cellulose; hemicellulose; ash composition and higher heating value were determined. We conducted a thermogravimetric analysis in oxidizing and inert atmospheres to study the behavior of the waste as fuel. The root productivity obtained ranged from 7.7 to 13.0 t ha−1 yr−1 on a dry basis (db), and the ratio between waste and roots varied from 0.36 to 0.91. The physical and chemical properties of cassava waste are analogous to those of woody biomass regarding the elemental composition, the higher heating value, and thermogravimetric analysis. Ash content varied from 2.5% to 3.5%, reaching around 6.0% in samples unwashed. Approximately 60% of the ashes are alkali oxides, especially P2O5, K2O, and CaO, which have low melting points. The alkali index calculated suggests that there is a strong tendency that the combustion process leads to ash fouling and the formation of ash deposits.

This work investigated the feasibility of using a blend of standard Brazilian diesel (which contains 5% biodiesel) and up to 5% ethanol. The mixture was characterized as fuel and the performance of a diesel engine operating with a blend containing 3% anhydrous ethanol, the maximum percentage of ethanol that did not reduce the cetane number of the fuel below that specified in Brazilian legislation (ANP Resolution 42), was measured. The presence of anhydrous ethanol in the mixture did not cause a significant impact on engine performance as measured by brake power, brake torque, and brake specific fuel consumption tests. The thermal efficiency of the engine used in the tests was slightly higher with standard diesel than with the diesel-biodiesel-ethanol blend.

So far there are no models to evaluate the entrainment flux and size distribution of FCC particles along the freeboard for large bubbling fluidized beds – BFB – taking into consideration particle agglomeration due to interparticle forces. A model was proposed to account for this phenomenon based on the available information, considering vertical ejection of particles due to bubble eruption on the bed surface and their trajectories' determination by Newton's second law. The model reproduced the exponential decay trend of the entrainment flux and, in general, estimated particle elutriation fluxes within a mean deviation of 15.82% and a maximum equal to 43.76% to those obtained experimentally. The model overestimated the size of the elutriated particles, with deviations ranging from 20.82 to 32.77%.

This work examines the entrainment of fluid cracking catalyst (FCC) particles from a large bubbling fluidized bed (BFB). An experimental setup consisting of a 0.60-m-inner diameter (i.d.), 5.5-m-high column, a high-efficiency Stairmand cyclone, a sampling valve and a movable conical top was designed and built to measure the entrainment mass rate as well as the size distribution of the FCC particles at several levels along the freeboard. To our knowledge, the size distribution has not previously been reported in the literature. The influence of superficial gas velocities in the range of 0.21 to 0.45 m/s was investigated. The results show that the entrainment rate had an exponential dependence on both freeboard height and superficial gas velocity. The size distribution analysis using dry sieving and a particle analyzer revealed that particle agglomeration occurred only in the dense bed and that neither segregation nor a reduction in particle size due to attrition and/or fragmentation took place.

El objetivo es mostrar la metodologia y resultados relacionados con el calculo de las velocidades de fluidizacion en un gasificador de lecho fluidizado burbujeante. Tambien se expone la caida de presion que sufre el agente de fluidizacion en el lecho de particulas. El calculo de las velocidades es importante, porque permite una buena fluidizacion lo que induce una distribucion uniforme de particulas. La buena distribucion de particulas provoca una distribucion uniforme de temperaturas en el gasificador donde se llevan a cabo las reacciones termoquimicas del proceso. La biomasa funciona como combustible del reactor y una correcta fluidizacion induce de manera resumida una correcta gasificacion. El buen calculo de la caida de presion en el lecho es vital para la correcta eleccion del soplador. Este es el dispositivo encargado de proporcionar la potencia y flujo de aire necesario para la fluidizacion. Las particulas del lecho son bauxita al 86% de alumina con una densidad de 2960kg/m^3 y un diametro medio de 1.5mm, el agente de fluidizacion es aire y el combustible usado son hojas trituradas de cana de azucar.

The proper disposal of electrical and electronic waste is currently a concern of researchers and environmental managers not only because of the large volume of such waste generated, but also because of the heavy metals and toxic substances it contains. This study analyzed printed circuit boards (PCBs) from discarded computers to determine their metal content and characterized them as solid waste and fuel. The analysis showed that PCBs consist of approximately 26% metal, made up mainly of copper, lead, aluminum, iron and tin, as well as other heavy metals such as cadmium and nickel. Comparison with the results of other studies indicated that the concentration of precious metals (gold and silver) has declined over time. Analysis of the leachate revealed high concentrations of cadmium and lead, giving the residue the characteristics of hazardous waste. After milling the PCBs, we found that larger amounts of metal were concentrated in smaller fractions, while the lightest fraction, obtained by density separation, had a gross calorific value of approximately 11 MJ/kg, although with a high ash content. Milling followed by density separation proved potentially useful for recovery of metals and energy-rich fractions.

Sugarcane bagasse is the residue produced by mills after juice is extracted from sugarcane. Other important solid residues in the sugarcane-to-sugar-and-ethanol production chain are the leaves and tops of the stalks (together referred to as cane trash). Although it represents a significant portion of the energy in sugarcane, cane trash is currently left in the fields. This paper has described and analyzed how residues (bagasse and cane trash) are produced from sugarcane and their use as an energy source in the production of ethanol. Also, it presents a review of the physical properties and characteristics of bagasse and cane trash and estimate their energy potential. Bagasse and cane trash have similar fuel characteristics to other biomasses fuels. Special attention should be given to the characteristics of cane trash ash, which has higher fusibility and alkali levels than bagasse. A flowchart of a typical mill was described and the thermal and mechanical energy consumption at various stages of the production process was determined. Of the energy consumed as work, about 58% is accounted for by milling and juice extraction, and 33% by the generation of electricity for use in the plant. In a typical mill using steam generators operating at average pressure and temperature (22 bar, 300–360 °C), about 15% of the bagasse produced is surplus, and an average of 480 kg of steam is used per tonne of cane processed. An energy consumption analysis revealed that there was significant scope for reducing the amount of steam needed to operate the turbines in mills because of the low isentropic efficiencies identified. Cane trash, which is not yet used for energy production, also shows great energy potential because it is produced in similar quantities to bagasse, and its calorific value is only slightly lower.

The spray tower is an industrial device widely employed for liquid–gas contact. In these towers, liquid is sprayed to generate droplets that provide a large interfacial area for heat and mass transfer between the continuous and dispersed phases. The performance of a spray tower is difficult to predict due to the complex hydrodynamics of system. This performance is influenced by several factors, such as droplet size and distribution, droplet velocity, collision and coalescence between droplets, internal recirculation, oscillation and distortion of the droplets, the relationship between different variables, and gas and liquid flow rates. Although spray towers are very common, there are few methodologies for their design, which is typically based on empirical or one-dimensional models. Experimental studies on gas absorption in spray towers have been carried out for years. However, all these studies used a single spray nozzle, whose configuration differs from that used in typical industrial spray towers, thus making the results of these studies difficult to apply in practice. The present work consisted of experimentally determining the volumetric mass transfer coefficient, kga, in a lab-pilot spray tower absorbing SO2, employing different operating conditions and two nozzle configurations, one involving the simultaneous use of a set of five spray nozzles and the other one, a single spray nozzle. New correlations to predict the coefficient kga are proposed, including two new parameters: the diameter of the spray nozzle orifice and the exit velocity of liquid from the orifice, as well as the superficial gas and liquid velocities, which have been used traditionally in other studies.

Spray towers are widely used for controlling air pollution by gases such as SO2, CO2, NOx, and HCl. Results of sulfur dioxide absorption in a spray tower using solutions of 1 g L–1 and 2 g L–1 of hydrogen peroxide are reported. For comparison, a water and sodium hydroxide solution was also used for SO2 abatement. The results indicate that H2O2 may be an important alternative for SO2 removal in spray towers. A set of experimental removal efficiency data was obtained as a function of gas and liquid flow rates. Volumetric mass transfer coefficients (kga) were calculated and an experimental relationship among kga, gas, and liquid flow rates was proposed. As a final experiment, an oxidation process assisted by UV radiation using a 1 g L–1 solution of H2O2 was carried out to speed up the SO2 removal rate. The results obtained in this condition are similar to those achieved with a solution of 2 g L–1 H2O2.

The inclusion of selective collection of urban residual solids in the public policies is an issue adopted by many countries as a mean for reducing the impacts created by solid waste generation and destination. In Brazil, the selective collection of solid waste was implemented in Campinas, in 1991. The city is the third biggest in the state of Sao Paulo and has a population of about a million inhabitants. The amount of recyclable matter amounts to 1% of the mixed solid waste collected by the public service and deposited in sanitary landfills. In the present study, reports and data forwarded by the municipality public service and the private cooperative units regarding the selective collection of solid waste are analyzed from the energy saving view point. The analysis showed that about 10,900 l of diesel oil are used to collect 329 ton/month of recyclables. The resulting energy economy is about 32 times the fuel energy used by the collecting trucks in the same period. This amount of recyclables led to an energy economy of 12,552 GJ/month, enough for a monthly equivalent electric consumption of 4000 residences.

The well-known kinetic mechanism of nitrogen oxides formation by thermal fixation of atmospheric nitrogen suggests the control of these pollutants by modifying the equivalence ratio and/or the temperature in the combustion region. In this experimental investigation a burner was specifically designed to take advantages of these chemical kinetic aspects. In particular, it was used to investigate the influence of swirl number and fuel equivalence ratio on nitric oxide concentration formed in a cylindrical combustion chamber. A set of 14 experimental runs was carried out to examine the influence of these factors, which were varied at seven and two levels (71 × 21) in the range of 0.36–1.32 and between 0.61 and 0.84, respectively. Liquefied petroleum gas (LPG) was always fired in the experiments. Temperature, O2 and NO concentration were monitored in 42 different radial and axial positions along the chamber at four different operating conditions in terms of NO formation. The effect of increasing the swirl number and reducing the fuel equivalence ratio was to reduce approximately 31% and 33% the nitric oxide emission, respectively.

Several fuel types have been used for cooking throughout the world, ranging from solid fuels to liquid to gas. Gaseous fuels are considered cleaner because of their inherent characteristics of low pollutant formation and emissions during handling and use. Nevertheless, from the viewpoint of sustainable development, other safety properties are important, such as flammability limits, auto-ignition temperature, specific gravity, vapour pressure, toxicity and flash point. This paper discusses several aspects of cooking fuel safety, considering traditional clean fuels such as LPG, natural gas and kerosene, and non-traditional and/or renewable fuels such as DME, producer gases, biosyngas, ethanol and ethanol-gel. The main aspects are related to transport and distribution system, product poisoning, equipment and use. Gaseous fuels are the preferred solution to replace unhealthy traditional fuels. As renewable options are still under development, LPG is often considered the short-term solution to deliver modern energy on a global scale for cooking applications.

A heat exchanger with a shallow gas–solid fluidized bed was experimentally studied in order to analyze energy recovery from solid particles leaving a combustion process. The experiments were carried out with and without vertical baffles in a fluidized bed with immersed horizontal tubes filled with water, in a counter flow arrangement. Two particle diameters (254 and 385 μm), two solid flow rates (50 and 80 kg/h) and two gas flow rates (46 and 50 kg/h) were tested. The bed temperature along the equipment length, the mass flow rate and the inlet and outlet temperatures of solid particles, air and water were measured in order to obtain the bed-tube heat transfer coefficient and the heat exchanger effectiveness. An increment of about 55% in the heat transfer coefficient and higher values of the heat exchanger effectiveness, in experiments with the presence of baffles, was verified. The experimental results also showed that the suspension-wall heat transfer coefficient increased considerably with the solid flow rate and also when the particle diameter decreased.

An electrolytic process for the removal of lead from aqueous solutions using a flow-through cell with a recycled niobium felt is proposed. The operational conditions for the reactor were optimised as a function of the solution flow rate and the electrolytic removal of Pb(II) was used to characterise the mass transport properties of the niobium felt electrode. The three-dimensional cathode was made from continuous niobium tips resulting from niobium ingots machining. The performance and figures of merit of the niobium felt were studied using different flow rates. In the experiments lead concentration dropped from 50 mg l −1 to 0.5 mg l −1 (99% removal) in electrolysis time ranging from 94 to 150 min, depending on the flow rate. Dimensionless Sherwood and Reynolds numbers were correlated to characterise the mass transport properties of the niobium felt, and they were fitted to the equation Sh =22.9( Re ) 0.43 ( Sc ) 0.33 .

Earth is exposed to an amount of energy that is fixed organically via photosynthesis and stored as fossil fuels, which are currently the major energy sources of humanity. Since Arrhenius concluded that carbon dioxide emissions from fossil fuels could lead to a climate warming, studies have sought ways to reduce human contribution on the environment to mitigate possible negative impacts on climate. The increasing world population is an obstacle for the efforts to reduce CO2 emissions and other greenhouse gases (GHG), because it demands more energy for transportation, electricity and heating. Among several renewable energy sources, biomass for fuels stands out, such as sugarcane ethanol in Brazil. Using biomass for fuels may help reducing the pressure on fossil fuels, besides, fixing organic carbon already emitted, contributing to mitigate problems of climate change and global warming. Thus, this study aims to analyse carbon cycles of mitigating emissions from fossil fuels with biofuel based on useful energy (exergy) content to determine the equivalent area required. Previous studies of life cycle assessment in sugarcane and eucalyptus were used to obtain carbon- and energy-flow data. These data were applied to estimate the available exergy to the final user through different routes of biofuel production, including current and evolving technologies. Exergy assessment demonstrated that on average, each Mg of biomass produced, led to a change of 3.02 GJ on sugarcane scenarios and 5.93 GJ on eucalyptus scenarios. Reducing sugarcane straw moisture from 50% to 30% increased the exergy output in 13.32 GJ ha-1, an increase of 0.67 GJ ha-1 for each 1% of moisture reduce. Eucalyptus to firewood, reducing moisture from 20% to 15% had an increase of 7.52 GJ ha-1 in the exergy output, representing 1.50 GJ ha-1 of increase for each 1%. This kind of assessment brings a new point of view in carbon mitigation, looking for its functionality. Biofuel use implications in environmental, social and economic aspects were also studied through a hybrid input-output life cycle assessment (IO-LCA) showing differences between the occupation of land use and two different ways of sugarcane production. The IO-LCA showed, in areas of land use change from pasture to sugarcane, energy consumption is increased by 3.7 times, employment is reduced by 5.4 times, and GHG emissions are reduced to only 2% of original emissions for each unit of R$ of final demand changed Most of the employment is generated by the sugarcane supply chain sector. Comparing sugarcane produced by the mills, it originates more direct full time jobs and probably in a more formal job market than sugarcane produced by farm suppliers. Farm suppliers use less energy and release less GHG than mills sugarcane production. A energia à qual o planeta é exposto é fixada organicamente via fotossíntese e estocado na forma de combustíveis fósseis, atualmente, as maiores fontes energéticas da humanidade. Desde que Arrhenius concluiu que emissões de CO2 decorrentes de combustíveis fósseis, poderiam levar a um aquecimento do clima, até os dias atuais, estudos buscam formas de reduzir os impactos antrópicos de forma a atenuar possíveis problemas climáticos. Os esforços para a redução de emissões de CO2 e outros gases de efeito estufa (GEE) têm como obstáculo uma população mundial crescente, que demanda cada vez mais energia para transporte, eletricidade e calor. Dentre as possibilidades de uso de fontes renováveis de energia, a biomassa é uma que se destaca em alguns países, como no caso do uso de etanol de cana-de-açúcar no Brasil. O uso de biomassa para a produção de combustíveis auxilia na redução da pressão para o uso de mais combustíveis fósseis e fixa organicamente o carbono emitido, contribuindo duplamente para a mitigação de problemas com mudanças climáticas e aquecimento global. O presente trabalho analisa os ciclos de carbono em biocombustível, correlacionando-os com sua energia útil (exergia) valorando a equivalência em área para a produção da exergia equivalente de combustíveis fósseis através de uma nova metodologia de avaliação de mitigação. Foram utilizados trabalhos existentes de análise de ciclo de vida em cana-de-açúcar e eucalipto para obtenção dos dados de inventário e fluxos de carbono e energia. Realizaram-se cálculos de exergia disponível ao usuário final com diferentes rotas de produção de biocombustível, abrangendo tecnologias atuais e em desenvolvimento. Na avaliação exergética, reduzir a humidade da palha da cana de 50% a 30% aumentou a exergia disponível em 13,32 GJ ha-1, 0,67 GJ ha-1 para cada 1% de redução na humidade. No caso do eucalipto para combustão, reduzindo-se a umidade de 20% a 15% houve um aumento de 7,52 GJ ha-1, 1,50 GJ ha-1 para cada 1% de umidade. Em média, cada Mg de biomassa produzida aumentou 3,02 GJ em cenários de cana de açúcar e 5,93 GJ em cenários de eucalipto. Este conceito traz uma nova perspectiva na mitigação de carbono, avaliando-o por sua funcionalidade. Também foram estudadas as implicações do uso de biocombustíveis em aspectos ambientais, sociais e econômicos em uma análise híbrida de ciclo de vida e insumo-produto (ACV-IP) evidenciando diferenças entre ocupação do uso de solo e duas maneiras de produção de cana-de-açúcar. A ACV-IP demonstrou que, em áreas de mudança do uso do solo de pastagem para cana de açúcar, o consumo de energia aumenta em 3,7 vezes, o emprego é reduzido em 5,4 vezes, e as emissões de GEE são reduzidas à apenas 2% das emissões originais para cada unidade de R$ de alteração na demanda final. A maior parte do emprego é gerado pelo setor da cadeia de suprimentos de produção de cana. A cana produzida pelas usinas origina mais empregos diretos do que a cana produzida por fornecedores agrícolas. Fornecedores usam menos energia e emitem menos GEE do que a produção de cana por usinas.

Este trabalho foi realizado junto ao NETeF - Núcleo de Engenharia Térmica e Fluídos da EESC/USP e ao aterro sanitário \"Fazenda Guaporé\" em São Carlos, e teve como objetivo a verificação da viabilidade energética e ambiental do tratamento do chorume através da sua incineração com o biogás produzido pelo aterro, eliminando-se desta forma também o metano, reconhecido como gás estufa. Determinou-se experimentalmente a composição do biogás e calculou-se e mediu-se a sua vazão. As propriedades físico-químicas e a vazão do chorume também foram quantificadas. A vazão de gás foi calculada com informações obtidas da literatura e medida experimentalmente com uma sonda especialmente desenvolvida neste trabalho. Para determinar a aplicabilidade do conceito fez-se um balanço energético para verificar a disponibilidade de energia e um balanço químico, para determinar o potencial de emissão de poluentes do ar. Os resultados indicaram que há mais energia presente no gás do que a energia requerida para incinerar o chorume, embora a diferença seja pequena e deva ser vista com cautela. O balanço químico mostrou em geral um potencial poluidor abaixo das emissões permitidas pela legislação, embora em alguns casos isto não tenha ocorrido. This work was developed at the NETeF (Thermal Engineering and Fluids Group) at EESC/USP, Sao Carlos, SP, and the local landfill \"Guapore Farm\". It was aimed to the treatment of the \"chorume\" through its incineration with the biogas produced in the landfill, this way eliminating also the methane, the second most important greenhouse gas according to IPCC. The composition and flow rate of the biogas were determined by calculations and experimentaly and the same was done with the chorume. The gas flowrate was calculated using data available in the literature and measured with a probe specially developed in this work. To evaluate the feasibility of the concept it was done a balance of energy to verify if the energy of the gas was enough to the chorume thermal destruction and a chemical balance to determinate the potential of emission of air pollutants. The results have shown that there is more energy available than it is required for that purpose but they should be considered with some caution given the small diference between the required and produced energy and the uncertaints in the measurements and evaluations. The chemical balance has shown that, in general, the potential for emissions was bellow the legally stablished limits although in a few cases it was above.